This invention is related to the electrode design of large area plasma display panels (PDPs) and, more particularly, to the use in PDPs of apertured electrodes with sparsely placed shorting bars to eliminate Moire effects and improve operating voltage uniformity.
Color plasma display panels (PDPs) are well known in the art. FIG. 1 illustrates a first prior art embodiment of an AC color PDP wherein narrow electrodes are employed on the front panel. More particularly, the AC PDP of FIG. 1 includes a front plate with horizontal plural sustain electrodes 10 that are coupled to a sustain bus 12. A plurality of scan electrodes 14 are juxtaposed to sustain electrodes 10, and both electrode sets are covered by a dielectric layer (not shown). A back plate supports vertical barrier ribs 16 and plural vertical column conductors 18 (shown in phantom). The individual column conductors are covered with red, green or blue phosphors, as the case may be, to enable a full color display to be achieved. The front and rear plates are sealed together and the space therebetween is filled with a dischargeable gas.
Pixels are defined by the intersections of (i) an electrode pair comprising a sustain electrode 10 and a juxtaposed scan electrode 14 on the front plate and (ii) three back plate column electrodes 18 for red, green and blue, respectively. Subpixels correspond to individual red, green and blue column electrodes that intersect with the front plate electrode pair.
Subpixels are addressed by applying a combination of pulses to both the front sustain electrodes 10 and scan electrodes 14 and one or more selected column electrodes 18. Each addressed subpixel is then discharged continuously (i.e., sustained) by applying pulses only to the front plate electrode pair. A PDP utilizing a similar front plate electrode structure is shown in U.S. Pat. No. 4,728,864 to Dick.
Operating voltages and power are controlled by the discharge gap and electrode width. The sustain and scan electrodes are placed to produce a narrow discharge gap and a wide inter-pixel gap. The discharge gap forms the center of the discharge site, and the discharge spreads out vertically. The inter-pixel gap must be made sufficiently large to prevent the spreading plasma discharge from corrupting the ON or OFF state of adjacent subpixels. The width of the electrode and the dielectric glass thickness over the electrode determine the pixel""s discharge capacitance which further controls the discharge power and therefore brightness. For a given discharge power/brightness, the number of discharges is chosen to meet the overall brightness requirement for the panel.
As display areas have increased, different methods have been employed to increase the pixel size. FIG. 2 illustrates an electrode structure which employs dual discharge sites per pixel and is the subject of U.S. patent application Ser. No. 08/939,251, to Applicant hereof and assigned to the same Assignee as this Application. Separate discharge sites (e.g., 20, 22) form between each pair of common scan electrodes (e.g., 24 and 26), and an address electrode 28. The discharges then spread across discharge gap C towards opposite sustain electrode loops (e.g., 30 and 32). Light output from each discharge site is emitted at discharge gap C and above and below the electrodes that form each discharge gap. With this electrode arrangement, there is a trade-off between electrode width and brightness because the electrodes tend to shade the emitted light.
FIG. 3 utilizes a wide transparent electrode to achieve both increased pixel capacitance and light output. Wide, transparent electrodes 40 are connected to sustain feed electrodes 10 and scan feed electrodes 42, 44, respectively. The discharge gap C between adjacent transparent electrodes 40 defines the electrical breakdown characteristic for the PDP. The width of electrodes 40 affects the pixel capacitance and, therefore, the discharge power requirements.
The light produced by a transparent electrode pair begins at the discharge gap and spreads out in both directions to and under the feed electrode 44. Since feed electrodes 10, 42 and 44 are at the edges of transparent electrodes 40, they tend to shade the light between pixel sites, producing dark horizontal lines between pixel rows. The wider transparent electrodes 40 provide a means to input greater power levels to the PDP for increased brightness. However, the manufacturing cost of transparent electrodes 40 is high due to the increased number of required processing steps.
The advantages provided by transparent electrodes are a high discharge capacitance and a large pixel area. The dual discharge site topology has low capacitance and therefore requires a greater number of discharge cycles to produce an equivalent amount of light as does the transparent electrode topology. Further, the light produced is concentrated to a very intense area at each discharge site, with additional light emitted between discharge sites. The transparent electrode topology thus produces a larger, brighter and more uniform discharge area than the dual discharge site topology, at the expense of cost.
It is an object of this invention to provide a PDP that exhibits enhanced light output.
It is another object of this invention to provide an improved PDP wherein light output characteristics of transparent electrode structures are achieved without incurring the higher manufacturing costs thereof.
It is a further object of this invention to provide an improved PDP that exhibits improved luminous efficiency.
An AC plasma display panel (PDP) incorporating the invention includes opposed substrates with an enclosed dischargeable gas positioned therebetween; plural elongated address electrodes positioned on one substrate; and plural scan electrode structures positioned on a second opposed substrate and orthogonally oriented to the address electrodes. A plurality of sustain electrode structures are positioned in parallel configuration and interdigitated with the scan electrode structures. Each sustain electrode structure and scan electrode structure is configured as an elongated conductive layer with plural apertures positioned therein. The elongated conductive layer, for each sustain electrode structure and each scan electrode structure, may be a cross-hatched conductor pattern or a plurality of parallel conductors connected by shorting bars.